1. Technical Field
The present invention relates to a pre-processing fluid, an ink set, an image forming apparatus, and an image forming method.
2. Background Art
The image density of an image is low when the image is formed on plain paper with an aqueous pigment ink discharged thereonto.
In attempts to solve this issue, a method has been introduced in which a pre-processing fluid is applied before an aqueous pigment ink is discharged.
However, a pre-processing fluid involves a problem of uneven coloring because the fluid has low level of wettability and defoambility.
A pre-processing fluid is known to improve these levels, which contains N-alkyl-2-pyrolidone, a fluorine-containing surfactant, and an acid or polyvalent metal salt. Materials having alkyl groups with 8 to 11 carbon atoms are used for N-alkyl-2-pyrolidone. In addition, for the fluorine-containing surfactant, compounds are used which are represented by a chemical formula: CnF2n+1—CH2CH(OH)CH2O—(CH2CH2O)a—Y, where n represents an integer of from 2 to 6, a represents an integer of from 15 to 50, Y represents a group represented by a chemical formula: —CbH2b+1, where b represents an integer of from 11 to 19 or a chemical formula: —CH2CH(OH)CH2—CmF2m+1, where m represents an integer of from 2 to 6, with a Hydrophile-Lipophile Balance (HLB) value of from 10 to 16 according to William C. Griffin.
However, subduing occurrence of uneven coloring is further demanded